Source of materialAsolution of nickel(II) acetate tetrahydrate (8.1 mg, 0.03 mmol) in ethanol (4 ml) was added dropwise to as olution of 3,3'-dimethoxy-2,2'-[(1,3-propylene)dioxybis(nitrilomethylidyne)]-diphenol (12.1 mg, 0.03 mmol) in acetone (30 ml). The color of the mixed solution turned to pale-green immediately, then the mixture was stirred for 1hatroom temperature. Finally, the solution was filtered, and the filtrate was allowed to stand at room temperature for about one week. When the solvent was partially evaporated, several green block-shaped single crystals suitable for X-ray crystallographic analysis were obtained.
Experimental detailsAll Hatoms were positioned geometrically with d(C-H) =0.93 -0.98 Å,and refined as riding with U iso(H) =1.2 or 1.5 Ueq(C). The aceton molecule and the ethyl group of an ethanol molecule are disordered with occupancies of 0.532(6) and 0.56(2) :0.44(2), respectively.
DiscussionTransition metal complexes with N,N'-disalicylideneethylenediamine (salen) ligand or its derivatives are extensively investigated, because these complexes have played aseminal role in the development of modern coordination chemistry. They can also be used in the design and construction of new magnetic materials and model of the metal center of enzymes. Although some advance has been made in the studies of salen-Ni(II) complexes [1-3], it still seems there could be new and specific applications for such aunique group of compounds. To change the structures or improve the functions of the resulted complexes, chemical modifications of the elemental salen-type ligand, e.g., introduction of some functional groups or appropriate substitution of some parts, are effective and inevitable. In particular, replacement of some atoms of the ligand with other elements often changes its properties drastically [4,5]. If an O-alkyloxime moiety (-CH=N-O-(CH 2)n-O-N=CH-)i su sed instead of the imine moiety, the larger electronegativity of oxygen atoms is expected to strongly affect the electronic properties of N 2 O 2 coordination sphere, which can lead to different and novel properties and structures of the resulted complexes [6,7]. Recently, we studied trinuclear complexes of cobalt [8,9]. The crystal structure contains al inear trinuclear array of three Ni(II) ions coupled by both doubly m-phenoxo oxygen atoms of (C 19 H 20 N 2 O 6 ) 2-units and simultaneously two acetate anions in the syn-syn bridging mode. The hexa-coordinated Ni(II) ions of the cluster have aslightly distorted octahedral coordination. The terminal nickel(II) ions (Ni2 and Ni2')are located in the N 2O2 coordination sphere of (C 19H20N2O6) 2-unit. One oxygen atom O8 from the m-acetato bridge and one oxygen atom O9 from the ethanol molecule are also coordinating Ni2. Consequently, the dihedral angle between the coordination plane of O5-Ni2-N1 and that of O3-Ni2-N2 is about 6.88(2)°,indicating slight distortion from the square planar toward octahedral geometry. In addition, the coordination sphere of the central nickel(II) ion (Ni1) is completed by q...